The advent of digital controllers has spurred the development of parallel-rectifier DC power systems. Such a system can exhibit a superior overall operating efficiency, because it varies the number of rectifiers it uses based on the load it is powering. Each rectifier in the system is capable of being placed in one of three states (or modes): an active, or operational, state; a stand-by state; and an inactive, or shut-down, state. The controller places the rectifiers in the active, stand-by, and inactive states depending upon the desired operating rectifier capacity determined by design, end-user preference or overall system operating condition. The controller keeps the number of active rectifiers to a minimum configured capacity threshold, which causes them to operate at a higher deterministic current level and, consequently, at a higher operating efficiency. Losses in the rectifiers that are in the inactive or stand-by states are quite low, perhaps zero.
As the load increases and reaches configurable operating capacity thresholds, the controller transitions rectifiers from the inactive state to the stand-by state or transitions rectifiers from the stand-by state to the active state. To keep efficiency as high as possible, the controller waits until the system load actually requires more power before it increases the number of active rectifiers. Fortunately, a battery reserve is available to provide any additional power needed during the interval when the rectifiers are transitioning from the inactive or stand-by states to the active state.